"This person often travels to the United States and has also been referred to as her "funder" throughout her correspondence", prosecutors said.
Robert Driscoll, a Washington lawyer representing Butina, told TIME in an email on Monday that his client was innocent and had been cooperating with "various government agencies for months".
They also wrote that Butina, who was indicted on Tuesday by a grand jury in Washington, D.C., has "access to funds and an intention to move money outside the United States".
An FBI affidavit submitted along with a criminal complaint against Butina last week said she and US Person 1 worked together to arrange introductions to other Americans who are influential in US politics, "including an organization promoting gun rights ... for the goal of advancing the agenda of the Russian Federation".
Image: The 29-year-old is charged with conspiracy.
The FBI said it has determined that even though Butina had a personal relationship with someone described in court papers as Person 1 - identified by NPR as political fundraiser Paul Erickson - she "offered an individual other than Person 1 sex in exchange for a position with a special interest organization".
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The Portland woman said she used a hose that fell off her vehicle to collect water dripping from moss to drink. She was last seen on CCTV at a filling station on 6 July, about 80km north of where she was found.
"Political Party 1" is likely the Republican party.
The NRA has so far made no comment this week about the charges against Butin or the Torshin connection.
"Butina is a Russian citizen with no meaningful ties to the United States; she has every reason to flee this prosecution", U.S. Attorney Jessie K. Liu wrote in the court document.
Her activities ramped up after she moved to the U.S. capital on a student visa in 2016, attending American University graduate school while she lived with Erickson.
In court documents filed earlier Wednesday, the feds allege that Butina dated a 56-year-old American man - believed to be South Dakota GOP strategist Paul Erickson - for his connections to the Republican Party and the National Rifle Association and also offered another USA citizen sex in exchange for a position in a "special interest organization".
"Because Butina has been exposed as an illegal agent of Russian Federation, there is the grave risk that she will appeal to those within that government with whom she conspired to aid her escape from the United States", the government's attorneys wrote.
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However, the description of the Russian official closely matches that of Alexander Torshin, a deputy governor of Russia's Central Bank who was sanctioned in April. But Donald Trump Jr. and Torshin did attend a separate NRA dinner the same night. Butina is also a gun rights activist in Russian Federation and a former gun store owner.
But by 2015 - well before Moscow's meddling in the 2016 election was exposed - Federal Bureau of Investigation counterintelligence agents saw her as an espionage threat.
Facebook Butina and Torshin seen with Wisconsin Gov. Scott Walker (R), center, at a campaign event in 2015.
"She kept showing up", Isikoff said, pointing to NRA events, a prayer breakfast and a Conservative Political Action Conference event reportedly attended by Butina.
The NRA has sought to downplay the extent of Russian-based financial contributions, but has yet to weigh in on Butina's arrest.
Butina's attorney, Robert Driscoll, has argued that Butina does not constitute a flight risk and should therefore not remain in jail ahead of a trial. He added that Butina voluntarily appeared "months ago" before the Senate Select Committee on Intelligence and "testified for 8 hours and produced thousands of documents".
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Prosecutors on Wednesday said Mariia Butina should be held in jail until her trial, because her life in the United States has been predicated on deception.